Controlling memory usage in a cache

ABSTRACT

Systems and methods for controlling cache usage are described and include associating, by a server computing system, a tenant in a multi-tenant environment with a cache cluster formed by a group of cache instances; associating, by the server computing system, a memory threshold and a burst memory threshold with the tenant; enabling, by the server computing system, each of the cache instances to collect metrics information based on the tenant accessing the cache cluster, the metrics information used to determine memory usage information and burst memory usage information of the cache cluster by the tenant; and controlling, by the server computing system, usage of the cache cluster by the tenant based on comparing the memory usage information with the memory threshold and comparing the burst memory usage information with the burst memory threshold.

COPYRIGHT NOTICE

A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.

TECHNICAL FIELD

The present disclosure relates generally to data processing and more specifically relates to caching associated with a multi-tenant environment.

BACKGROUND

The subject matter discussed in the background section should not be assumed to be prior art merely as a result of its mention in the background section. Similarly, a problem mentioned in the background section or associated with the subject matter of the background section should not be assumed to have been previously recognized in the prior art. The subject matter in the background section merely represents different approaches, which in and of themselves may also be inventions.

In general, caching may improve performance. Careful management of the content of the cache is important to maintain its effectiveness. When caching is used in a multi-tenant environment, the management of the cache becomes more complex because each of the tenants may have different management requirements.

BRIEF SUMMARY

For some embodiments, systems and methods for controlling memory usage in a cache may include associating, by a server computing system, a tenant in a multi-tenant environment with a cache cluster formed by a group of cache instances; associating, by the server computing system, a memory threshold and a burst memory threshold with the tenant; enabling, by the server computing system, each of the cache instances to collect metrics information based on the tenant accessing the cache cluster, the metrics information used to determine memory usage information and burst memory usage information of the cache by the tenant; and controlling, by the server computing system, usage of the cache by the tenant based on comparing the memory usage information with the memory threshold and comparing the burst memory usage information with the burst memory threshold. Other aspects and advantages of the present invention can be seen on review of the drawings, the detailed description and the claims, which follow.

BRIEF DESCRIPTION OF THE DRAWINGS

The included drawings are for illustrative purposes and serve only to provide examples of possible structures and process steps for the disclosed techniques. These drawings in no way limit any changes in form and detail that may be made to embodiments by one skilled in the art without departing from the spirit and scope of the disclosure.

FIG. 1 shows a diagram of an example computing system that may be used with some embodiments.

FIG. 2A shows a diagram of an example network environment that may be used with some embodiments.

FIG. 2B shows a diagram of an example of a network environment that may include a cache system, in accordance with some embodiments.

FIG. 3 shows a diagram of an example cache cluster, in accordance with some embodiments.

FIG. 4A and FIG. 4B show an example diagram of a cache instance and metering module associated with the cache instance, in accordance with some embodiments.

FIG. 5 shows a diagram of example a cache client and a message bus, in accordance with some embodiments.

FIG. 6 shows a diagram of a cache system that may be used with a multi-tenant environment, in accordance with some embodiments.

FIG. 7 is an example flowchart that shows execution of cache management system in a multi-tenant environment, in accordance with some embodiments.

FIG. 8A shows a system diagram illustrating architectural components of an applicable environment, in accordance with some embodiments.

FIG. 8B shows a system diagram further illustrating architectural components of an applicable environment, in accordance with some embodiments.

FIG. 9 shows a system diagram illustrating the architecture of a multi-tenant database environment, in accordance with some embodiments.

FIG. 10 shows a system diagram further illustrating the architecture of a multi-tenant database environment, in accordance with some embodiments.

DETAILED DESCRIPTION

Systems and methods for controlling cache resources when cache instances are used for tenants in a multi-tenant environment are disclosed. Each tenant may be associated with a burst memory threshold and a memory threshold. Metrics information may be collected by each cache instance associated with the tenant. Aggregated metrics information may be generated to enable performing controlling of the cache resources. Evictions may be performed when the memory threshold is violated. Pausing of cache-write related operations by the tenant may occur when the burst memory threshold is violated.

The systems and methods associated with managing cache resources by tenants using cache instances will be described with reference to example embodiments. These examples are being provided solely to add context and aid in the understanding of the present disclosure. It will thus be apparent to one skilled in the art that the techniques described herein may be practiced without some or all of these specific details. In other instances, well known process steps have not been described in detail in order to avoid unnecessarily obscuring the present disclosure. Other applications are possible, such that the following examples should not be taken as definitive or limiting either in scope or setting.

In the following detailed description, references are made to the accompanying drawings, which form a part of the description and in which are shown, by way of illustration, specific embodiments. Although these embodiments are described in sufficient detail to enable one skilled in the art to practice the disclosure, it is understood that these examples are not limiting, such that other embodiments may be used and changes may be made without departing from the spirit and scope of the disclosure.

As used herein, the term “multi-tenant database system” refers to those systems in which various elements of hardware and software of the database system may be shared by one or more customers. For example, a given application server may simultaneously process requests for a great number of customers, and a given database table may store rows for a potentially much greater number of customers.

The described subject matter may be implemented in the context of any computer-implemented system, such as a software-based system, a database system, a multi-tenant environment, or the like. Moreover, the described subject matter may be implemented in connection with two or more separate and distinct computer-implemented systems that cooperate and communicate with one another. One or more embodiments may be implemented in numerous ways, including as a process, an apparatus, a system, a device, a method, a computer readable medium such as a computer readable storage medium containing computer readable instructions or computer program code, or as a computer program product comprising a computer usable medium having a computer readable program code embodied therein.

The disclosed embodiments may include a method for controlling memory usage in a cache and may include associating, by a server computing system, a tenant in a multi-tenant environment with a cache formed by a group of cache instances in a cache cluster; associating, by the server computing system, a memory threshold and a burst memory threshold with the tenant; enabling, by the server computing system, each of the cache instances to collect metrics information based on the tenant accessing the cache, the metrics information used to determine memory usage information and burst memory usage information of the cache by the tenant; and controlling, by the server computing system, usage of the cache by the tenant based on comparing the memory usage information with the memory threshold and comparing the burst memory usage information with the burst memory threshold.

The disclosed embodiments may include a system for controlling memory usage in a cache and may include one or more processors; and a non-transitory computer readable medium storing a plurality of instructions, which when executed, cause the one or more processors of a server computing to associate a tenant in a multi-tenant environment with a cache formed by a group of cache instances in a cache cluster; associate a memory threshold and a burst memory threshold with the tenant; enable each of the cache instances to collect metrics information based on the tenant accessing the cache, the metrics information used to determine memory usage information and burst memory usage information of the cache by the tenant; and control usage of the cache by the tenant based on comparing the memory usage information with the memory threshold and comparing the burst memory usage information with the burst memory threshold.

The disclosed embodiments may include a computer program product comprising computer-readable program code to be executed by one or more processors of a server computing system when retrieved from a non-transitory computer-readable medium, the program code including instructions to associate a tenant in a multi-tenant environment with a cache formed by a group of cache instances in a cache cluster; associate a memory threshold and a burst memory threshold with the tenant; enable each of the cache instances to collect metrics information based on the tenant accessing the cache, the metrics information used to determine memory usage information and burst memory usage information of the cache by the tenant; and control usage of the cache by the tenant based on comparing the memory usage information with the memory threshold and comparing the burst memory usage information with the burst memory threshold.

While one or more implementations and techniques are described with reference to an embodiment relating to a cache implemented in a system having an application server providing a front end for an on-demand database service capable of supporting multiple tenants, the one or more implementations and techniques are not limited to multi-tenant databases nor deployment on application servers. Embodiments may be practiced using other database architectures, i.e., ORACLE®, DB2® by IBM and the like without departing from the scope of the embodiments claimed.

Any of the above embodiments may be used alone or together with one another in any combination. The one or more implementations encompassed within this specification may also include embodiments that are only partially mentioned or alluded to or are not mentioned or alluded to at all in this brief summary or in the abstract. Although various embodiments may have been motivated by various deficiencies with the prior art, which may be discussed or alluded to in one or more places in the specification, the embodiments do not necessarily address any of these deficiencies. In other words, different embodiments may address different deficiencies that may be discussed in the specification. Some embodiments may only partially address some deficiencies or just one deficiency that may be discussed in the specification, and some embodiments may not address any of these deficiencies.

The described subject matter may be implemented in the context of any computer-implemented system, such as a software-based system, a database system, a multi-tenant environment, or the like. Moreover, the described subject matter may be implemented in connection with two or more separate and distinct computer-implemented systems that cooperate and communicate with one another. One or more implementations may be implemented in numerous ways, including as a process, an apparatus, a system, a device, a method, a computer readable medium such as a computer readable storage medium containing computer readable instructions or computer program code, or as a computer program product comprising a computer usable medium having a computer readable program code embodied therein.

FIG. 1 is a diagram of an example computing system that may be used with some embodiments of the present invention. The computing system 102 may be used by a user to log into a server computing system to cause the server computing system to perform operations on behalf of the user. For example, the user may use a web browser to access web services provided by the server computing system. For some embodiments, the server computing system may be associated with a multi-tenant database environment. For example, the multi-tenant database environment may be associated with the services provided by Salesforce.com®.

The computing system 102 is only one example of a suitable computing system, such as a mobile computing system, and is not intended to suggest any limitation as to the scope of use or functionality of the design. Neither should the computing system 102 be interpreted as having any dependency or requirement relating to any one or combination of components illustrated. The design is operational with numerous other general purpose or special purpose computing systems. Examples of well-known computing systems, environments, and/or configurations that may be suitable for use with the design include, but are not limited to, personal computers, server computers, hand-held or laptop devices, multiprocessor systems, microprocessor-based systems, set top boxes, programmable consumer electronics, mini-computers, mainframe computers, distributed computing environments that include any of the above systems or devices, and the like. For example, the computing system 102 may be implemented as a mobile computing system such as one that is configured to run with an operating system (e.g., iOS) developed by Apple Inc. of Cupertino, Calif. or an operating system (e.g., Android) that is developed by Google Inc. of Mountain View, Calif.

Some embodiments of the present invention may be described in the general context of computing system executable instructions, such as program modules, being executed by a computer. Generally, program modules include routines, programs, objects, components, data structures, etc. that performs particular tasks or implement particular abstract data types. Those skilled in the art can implement the description and/or figures herein as computer-executable instructions, which can be embodied on any form of computing machine program product discussed below.

Some embodiments of the present invention may also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules may be located in both local and remote computer storage media including memory storage devices.

Referring to FIG. 1, the computing system 102 may include, but are not limited to, a processing unit 120 having one or more processing cores, a system memory 130, and a system bus 121 that couples various system components including the system memory 130 to the processing unit 120. The system bus 121 may be any of several types of bus structures including a memory bus or memory controller, a peripheral bus, and a local bus using any of a variety of bus architectures. By way of example, and not limitation, such architectures include Industry Standard Architecture (ISA) bus, Micro Channel Architecture (MCA) bus, Enhanced ISA (EISA) bus, Video Electronics Standards Association (VESA) locale bus, and Peripheral Component Interconnect (PCI) bus also known as Mezzanine bus.

The computing system 102 typically includes a variety of computer program product. Computer program product can be any available media that can be accessed by computing system 102 and includes both volatile and nonvolatile media, removable and non-removable media. By way of example, and not limitation, computer program product may store information such as computer readable instructions, data structures, program modules or other data. Computer storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by computing system 102. Communication media typically embodies computer readable instructions, data structures, or program modules.

The system memory 130 may include computer storage media in the form of volatile and/or nonvolatile memory such as read only memory (ROM) 131 and random access memory (RAM) 132. A basic input/output system (BIOS) 133, containing the basic routines that help to transfer information between elements within computing system 102, such as during start-up, is typically stored in ROM 131. RAM 132 typically contains data and/or program modules that are immediately accessible to and/or presently being operated on by processing unit 120. By way of example, and not limitation, FIG. 1 also illustrates operating system 134, application programs 135, other program modules 136, and program data 137.

The computing system 102 may also include other removable/non-removable volatile/nonvolatile computer storage media. By way of example only, FIG. 1 also illustrates a hard disk drive 141 that reads from or writes to non-removable, nonvolatile magnetic media, a magnetic disk drive 151 that reads from or writes to a removable, nonvolatile magnetic disk 152, and an optical disk drive 155 that reads from or writes to a removable, nonvolatile optical disk 156 such as, for example, a CD ROM or other optical media. Other removable/non-removable, volatile/nonvolatile computer storage media that can be used in the exemplary operating environment include, but are not limited to, USB drives and devices, magnetic tape cassettes, flash memory cards, digital versatile disks, digital video tape, solid state RAM, solid state ROM, and the like. The hard disk drive 141 is typically connected to the system bus 121 through a non-removable memory interface such as interface 140, and magnetic disk drive 151 and optical disk drive 155 are typically connected to the system bus 121 by a removable memory interface, such as interface 150.

The drives and their associated computer storage media discussed above and illustrated in FIG. 1, provide storage of computer readable instructions, data structures, program modules and other data for the computing system 102. In FIG. 1, for example, hard disk drive 141 is illustrated as storing operating system 144, application programs 145, other program modules 146, and program data 147. Note that these components can either be the same as or different from operating system 134, application programs 135, other program modules 136, and program data 137. The operating system 144, the application programs 145, the other program modules 146, and the program data 147 are given different numeric identification here to illustrate that, at a minimum, they are different copies.

A user may enter commands and information into the computing system 102 through input devices such as a keyboard 162, a microphone 163, and a pointing device 161, such as a mouse, trackball or touch pad or touch screen. Other input devices (not shown) may include a joystick, game pad, scanner, or the like. These and other input devices are often connected to the processing unit 120 through a user input interface 160 that is coupled with the system bus 121, but may be connected by other interface and bus structures, such as a parallel port, game port or a universal serial bus (USB). A monitor 191 or other type of display device is also connected to the system bus 121 via an interface, such as a video interface 190. In addition to the monitor, computers may also include other peripheral output devices such as speakers 197 and printer 196, which may be connected through an output peripheral interface 190.

The computing system 102 may operate in a networked environment using logical connections to one or more remote computers, such as a remote computer 180. The remote computer 180 may be a personal computer, a hand-held device, a server, a router, a network PC, a peer device or other common network node, and typically includes many or all of the elements described above relative to the computing system 102. The logical connections depicted in

FIG. 1 includes a local area network (LAN) 171 and a wide area network (WAN) 173, but may also include other networks. Such networking environments are commonplace in offices, enterprise-wide computer networks, intranets and the Internet.

When used in a LAN networking environment, the computing system 102 may be connected to the LAN 171 through a network interface or adapter 170. When used in a WAN networking environment, the computing system 102 typically includes a modem 172 or other means for establishing communications over the WAN 173, such as the Internet. The modem 172, which may be internal or external, may be connected to the system bus 121 via the user-input interface 160, or other appropriate mechanism. In a networked environment, program modules depicted relative to the computing system 102, or portions thereof, may be stored in a remote memory storage device. By way of example, and not limitation, FIG. 1 illustrates remote application programs 185 as residing on remote computer 180. It will be appreciated that the network connections shown are exemplary and other means of establishing a communications link between the computers may be used.

It should be noted that some embodiments of the present invention may be carried out on a computing system such as that described with respect to FIG. 1. However, some embodiments of the present invention may be carried out on a server, a computer devoted to message handling, handheld devices, or on a distributed system in which different portions of the present design may be carried out on different parts of the distributed computing system.

Another device that may be coupled with the system bus 121 is a power supply such as a battery or a Direct Current (DC) power supply) and Alternating Current (AC) adapter circuit. The DC power supply may be a battery, a fuel cell, or similar DC power source needs to be recharged on a periodic basis. The communication module (or modem) 172 may employ a Wireless Application Protocol (WAP) to establish a wireless communication channel. The communication module 172 may implement a wireless networking standard such as Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard, IEEE std. 802.11-1999, published by IEEE in 1999.

Examples of mobile computing systems may be a laptop computer, a tablet computer, a Netbook, a smart phone, a personal digital assistant, or other similar device with on board processing power and wireless communications ability that is powered by a Direct Current (DC) power source that supplies DC voltage to the mobile computing system and that is solely within the mobile computing system and needs to be recharged on a periodic basis, such as a fuel cell or a battery.

FIG. 2A shows a diagram of an example network environment that may be used with some embodiments of the present invention. Network environment 200 includes computing systems 290 and 291. One or more of the computing systems 290 and 291 may be a mobile computing system. The computing systems 290 and 291 may be connected to the network 250 via a cellular connection or via a Wi-Fi router (not shown). The network 250 may be the Internet. The computing systems 290 and 291 may be coupled with server computing systems 255 via the network 250. Each of the computing systems 290 and 291 may include an application module such as module 208 or 214. For example, a user may use the computing system 290 and the application module 208 to connect to and communicate with the server computing system 255 and log into application 257 (e.g., a Salesforce.com® application). The server computing system 255 may be a web server configured to accept and respond to Hypertext Transfer Protocol (HTTP) requests. A client (e.g., a browser) from the computing system 290 or 291 may open a connection to the server computing system 255 and sends a request. The server computing system 255 may process the request and generate a response. It is possible that the server computing system 255 may receive many requests concurrently, and processing and responding to those requests may affect the overall performance of the server computing system 255.

FIG. 2B shows a diagram of an example of a network environment that may include a cache system, in accordance with some embodiments. Network environment 201 may be similar to the network environment 200 of FIG. 2A except with the addition of the cache system 280. The cache system 280 may be associated with the server computing system (e.g., web server) 255. The cache system 280 may be implemented using a combination of hardware and software. The cache system 280 may include memory 285 (also referred to as a cache) configured to store data that is frequently requested from the server computing system 255. For example, when a request for data is received, and the data is already stored in the cache 285, the data may be retrieved from the cache 285. Different policies may be used to manage the content of the cache 285. For example, when the cache 285 is full, an eviction policy may be applied to the content to remove some existing data to create space for new data. The eviction policy may be based on, for example, least recently used (LRU) or least frequently used (LFU). Although the diagram 201 shows one cache system 280 and one server computing system 255, the cache system 280 may span over more than one computing system to provide caching services to multiple server computing systems.

FIG. 3 shows a diagram of an example cache cluster, in accordance with some embodiments. The cache system 280 (shown in FIG. 2B) may include one or more cache clusters including, for example, cache cluster 305. The cache cluster 305 in diagram 300 may include one or more cache instances 310A-310N. The one or more cache instances 310A-310N may work together as one logical cache. For example, the cache 285 (shown in FIG. 2B) may be a logical cache.

The one or more cache instances 310A-310N may be configured to respond to requests from the computing systems 290 and 291 (shown in FIG. 2B). The one or more cache instances 310A-310N may be configured to receive data from the server computing system 255 (shown in FIG. 2B). Each of the cache instances 310A-310N may include a portion of the content of the logical cache.

For some embodiments, in a multi-tenant environment, a tenant may be associated with a logical cache formed by a group of cache instances. A tenant may be an organization, a set of organizations, a feature, etc. A tenant may be a uniquely identifiable user of a cache. This may enable the cache content associated with a tenant to be distributed among the multiple cache instances, thus improving cache performance when multiple data update requests are generated by the tenant. For example, the computing systems 290 and 291 (shown in FIG. 2B) may be associated with a tenant. The cache cluster 305 may define the policies which are applied to all the cache instances 310A-310N. For example, the policies may include specifying the portion of the cache content that a cache instance is responsible for, among others. When a request is received from the tenant, the request may be sent to a particular cache instance based on the cache content that the cache instance is responsible for. If there is a cache hit, the request may be processed by the cache instance. If there is a cache miss, the request may be forwarded to the server computing system 255 (shown in FIG. 2B)

FIGS. 4A-4B show example diagrams of a cache instance and metering module associated with cache instances in a cache cluster, in accordance with some embodiments. Diagram 400 includes a cache instance 405 which may include a tenant-ID extractor 410, command module 415, metrics information 420 and memory 425. The tenant-ID extractor 410 may be configured to extract the tenant ID of the tenant associated with the cache instance 405. As described with FIG. 3, in a multi-tenant environment, a tenant may be associated with a group of cache instances. Further, a cache instance may be configured to store data associated with one or more tenants in memory 425.

A unique cache key may be associated with a content of the memory 425. The unique cache key may include a tenant ID. For example, the cache key may have the following format <TenantID><Key> where the tenant ID is a prefix of the cache key. The tenant ID may also be obtained by other means such as, for example, using one connection per tenant so that the tenant ID may need to be extracted only once when the connection is established. The cache key, along with other elements, may be used to form an identifier that is associated with a value stored in a cache. The same identifier may be used to retrieve the same value from the memory 425.

For some embodiments, command metadata may be included at the end of a command. For example, the command may be related to cache write operations on behalf of a specific tenant. The command metadata may be used to provide the tenant ID instead of using a prefix of the cache key. The tenant ID may be part of the tenant-related information that can be included in the command metadata.

The command module 415 may include eviction command and get metrics information command. The eviction command may include operations to evict certain content of the cache that the cache instance 405 is responsible for per tenant basis. In order to support the eviction operations, the cache instance 405 is configured to maintain an index of keys per tenant. The eviction strategy may dictate the internal data structure/sort order used to store the key index. The index may be stored in memory. The index may be constantly updated per tenant via the synchronous interceptor events (e.g., set/put/delete/expire). A sort order may be selected based on the eviction strategy (e.g., LRU/LFU).

For some embodiments, the eviction command may have the following format: Evict-Tenant (Tenant-ID, Memory-size, MaxTime). The eviction command may use the key index which is already sorted in the required order and keeps deleting the key-value pairs from the cache until the amount of deleted memory reaches the command parameter “Memory-size” or when the time spent processing the eviction command reaches the command parameter “MaxTime.” The “MaxTime” parameter may help ensuring that the eviction process does not block incoming calls (e.g., cache write operations), especially for single threaded cache implementations. When either of the “Memory-size” and “MaxTime” is met, the processing of the eviction command may stop.

The get-metrics information command may include operations to collect metrics information 420 for the tenant associated with the cache instance 405. The metrics information 420 may include usage metrics such as, for example, memory used or number of operations which needs to be measured per tenant. For some embodiments, the collection of the metrics information 420 may be performed using synchronous interceptor callbacks on cache-write related operations (e.g., set, update, increment, and decrement), cache evictions and updates. The get-metrics operations may get the tenant ID using either the cache key prefix or the command metadata depending on the implementation.

For some embodiments, the get-metrics operations may collect per-tenant metrics information 420 based on the incoming key per cache instance. The metrics information may be used to determine an amount of memory used per tenant from the memory 425 (see Table 1 below). The metrics information may include information about time spent per tenant in processing cache related commands. For example, on an update of a key, the synchronous interceptor may update the amount of memory used per tenant with the difference in the value size before and after the update. In the case of an eviction interceptor, the amount of memory used by a tenant may be reduced after the eviction operations.

A list of tenants associated with a cache instance may be maintained. The list of tenants may be updated periodically when the amount of memory associated with a tenant is reduced to zero so that the appropriate tenant ID can be removed from the list. Table 1 below shows an example list of tenants implemented using a hash table.

TABLE 1 Tenant ID (hash table) Memory Usage Tenant 1 Xxx bytes Tenant 2 Yyy bytes Tenant n Zzz bytes

The metering module 450 may be associated with a cache cluster. The metering module 450 may be configured to periodically pull or receive the metrics information 420 from the cache instance 405 associated with the cache cluster and computes the necessary aggregation with other cache instances. For some embodiments, the metering module 450 may be configured to collect the metrics information at the tenant level based on incoming cache key per cache instance.

When the cache cluster 305 includes multiple cache instances, each of the cache instances in the cache cluster may be configured to transmit its metrics information to the metering module 450. For some embodiments, the metering module 450 may be configured to maintain information about the tenants associated with the cache cluster 305 and the metrics information associated with each tenant.

The metering module 450 may also be configured to maintain information about a memory threshold and a burst memory threshold per tenant. The memory threshold may correspond to a maximum amount of memory that is set for a tenant. This may be a steady state maximum memory. The burst memory threshold may correspond to a maximum burst memory set for the tenant. The burst memory threshold may be a temporary and acceptable peak memory usage but may not be a steady state memory usage. For example, when the memory usage reaches the memory threshold, the burst memory threshold may be the max memory that a tenant can use before pausing its operation.

Both the memory threshold and the burst memory threshold are configurable settings provisioned by a system administrator. The burst memory threshold is usually greater than the memory threshold. For example, the burst memory threshold may be based on a certain percentage (e.g., 50%) greater than the memory threshold. Table 2 below shows example tenant memory usage information. Column 4 shows a total current memory usage per tenant. Column 5 shows a list of current memory usage by each tenant broken down to each cache instance in a cluster. C1 corresponds to a first cache instance, and C2 corresponds to a second cache instance, etc. The information in the columns 4 and 5 may be periodically updated. For example, each cache instance may be configured to periodically transmit the usage information to the metering module 450. The metering module 450 may also be configured to collect information about time spent to process cache-write related operations per tenant.

TABLE 2 Burst- Total Current List Tenant Memory Memory Memory <CacheInstanceID: ID Threshold Threshold Usage Memory-Usage> Tenant 1 GB 1.5 GB   3 GB <C1: 0.2 GB, 1 C2: 0.41 GB, . . . > Tenant 1.5 GB   2.25 GB  1.8 GB <C1: 0.11 GB, 2 C2: 0.131 GB, . . . > Tenant .2 GB   .3 GB .15 GB <C1: 0.32 GB, 3 C2: 0.123 GB, . . . > Tenant 2 GB 3.0 GB 1.4 GB <C1: 0.02 GB, n C2: 0.183 GB, . . . >

The metering module 450 may be configured to monitor and enforce the memory threshold and the burst memory threshold shown in Table 2 for each tenant. For example, the metering module 450 may use the memory threshold and the memory usage information to determine a list of tenant that are using more memory than set by the system administrator. A percentage of the memory used over the memory threshold may be determined, and the list of tenants may be ordered based on the percentage. For example, the list may show that a tenant at the top is using 25% more memory than the memory threshold, a next tenant is using 10% more, etc.

For each tenant, a memory threshold per cache instance may be determined using the memory threshold for the tenant. This is shown in the following Formula 1: Memory Threshold Per Cache Instance=Memory Threshold for a tenant/Number of cache instances associated with the tenant   Formula 1 The determination of the memory threshold per cache instance of formula 1 assumes a uniform distribution. However, the actual memory usage may not be uniform across all the cache instances. For some embodiments, an enhanced memory threshold per cache instance may be determined using the result of the above Formula 1. This is shown in the following Formula 2: Enhanced Memory Threshold Per Cache Instance=Memory Threshold Per Cache Instance+(aggregate of memory differences of cache instances with current memory usage less than the memory threshold per cache instance)/(number of cache instances with current memory usage more than the memory threshold setting per cache instance)   Formula 2 When the current memory usage of a tenant in a cache instance violates or exceeds the enhanced memory threshold per cache instance, eviction may occur by using the following example eviction command: Call Evict_tenant (TenantID, Current Memory Usage in a Cache Instance—Enhanced Memory Threshold Per Cache Instance). The eviction may be applied to each of the cache instances where the memory usage violates or exceeds the enhanced memory threshold. This provides memory usage control at the cache instance level.

The metering module 450 may be configured to monitor a burst memory usage by a tenant and compare that with the burst memory threshold (as shown in column 3 of Table 2). The burst memory usage may correspond to a temporary memory usage that exceeds a normal steady state memory usage. For some embodiments, the metering module 450 may generate a list of tenants whose burst memory usage exceeds the burst memory threshold using the per tenant cluster-wide aggregated metrics information. For each tenant on this list, the metering module 450 may cause the tenant to pause cache-write related operations for a certain length of time. This provides control at the ingress to the cache at the cache instance level. For example, the metering module 450 may generate a pause message using the format {tenantID, PAUSE TENANT WRITE, pause period} to request a tenant to pause cache-write related operations for up to the pause period. For some embodiments, after the burst memory usage stops violating (e.g., is at or below) the burst memory threshold, the metering module 450 may be configured to clear the list of tenants whose burst memory usage violated (e.g., exceeded) the burst memory threshold. For each tenant on the list, the metering module 450 may cause the tenant to resume their cache-write related operations. For example, the metering module 450 may generate a resume message using the format {tenantID, RESUME TENANT WRITE} to indicate that cache-write related operations can be resumed.

FIG. 5 shows a diagram of an example cache client and a message bus, in accordance with some embodiments. In diagram 500, cache client 505 may be configured to monitor for events on message bus 508 and perform operations on a per tenant basis. For example, the cache client 505 may listen for back pressure signals from the message bus 508. Back pressure signals may include signals that cause cache-write related operations to be paused. The cache client 505 may maintain a paused tenants hash table 510 configured to include a list of tenants and their current state. For example, the list of tenants may be ordered based on the tenant ID, and the current state may be pause and the pause period. Although not shown, there may also be a start time for each pause period to determine the expiration of the pause period. Based on expiration of the pause period, the tenant may be removed from the list. If a tenant ID of a tenant is not on the list of the paused tenants hash table 510, it may be understood that there no pausing or back pressure needs to be applied to that tenant. For some embodiments, the pause period may be determined individually for each tenant. Thus, it may be possible for two tenants to be associated with two different pause periods.

For some embodiments, the cache client 505 may be configured to receive signals from the metering module 450 (shown in FIG. 4) to update the paused tenants hash table 510. For example, after the metering module 450 generate the pause message {tenantID, PAUSE TENANT WRITE, pause period}, that pause message may be sent to the message bus 508 and received by the cache client 505. Based on the tenantID and the pause period parameters included in the message, the cache client 505 may then update the paused tenants hash table 510 to include the tenant ID and the pause period. Similarly, after the metering module 450 generate the resume message {tenantID, RESUME TENANT WRITE}, that resume message may be sent to the message bus 508 and received by the cache client 505. Based on the tenantID included in the message, the cache client 505 may then update the paused tenants hash table 510 to remove the tenant ID. The cache client 505 may be configured to receive cache write request 555 from a tenant and process the cache write request 555 using the paused tenants hash table 508.

FIG. 6 shows a diagram of a cache system that may be used with a multi-tenant environment, in accordance with some embodiments. Diagram 600 is shown with components of a cache system similar to the cache system 280 shown in FIG. 2B. Cache system 280 may include multiple cache clients 605A-605N. Each of the cache clients may be configured to interact with a set of tenants. Multiple cache write requests 650 may be received by the cache clients 605A-605N. A cache client may store information about whether a tenant is in a pause state based on back pressure information received from the message bus 508. The back pressure information may be provided by the metering module 655 based on how much memory is being used by the cache instances 615A-615N associated with that tenant.

The back pressure information may include information to pause the cache write operations and information to resume the cache write operations. If a cache write request is received from a tenant who is in a pause state, the cache write request may be dropped. Further, if a tenant is in a pause state, the cache client 505 may verify a pause period and a corresponding pause period start time to determine if the pause period has expired for that tenant. If the pause period has not expired, the cache write request may be dropped. If the pause period has expired or if the tenant does not exist on the list, the cache write request may be allowed to proceed. For some embodiments, the metering module 655 may be configured to transmit the back pressure signals directly to the cache clients 605A-605N instead of to the message bus 508. Line 690 is shown to indicate that a cache client may directly communicate with a cache instance for cache operation.

FIG. 7 is an example flowchart that shows execution of cache management system in a multi-tenant environment, in accordance with some embodiments. Flow diagram 700 may be used to manage a cache in a multi-tenants environment. The flow diagram may start at block 705. At block 710, a group of cache instances in a cache cluster may be associated with a tenant. At block 715, a memory threshold and a burst memory threshold may be associated with the tenant. The memory threshold may correspond to a maximum amount of memory configured for the tenant, and the burst memory threshold may correspond to a maximum burst memory configured for the tenant.

At block 720, eviction operations may be performed using an eviction policy (e.g., LRU/LFU). As described with FIG. 4, the eviction may be performed by using the Evict command of the command module 415.

At block 725, each of the cache instances may be configured to get metrics information based on the usage by the tenant. As described with FIG. 4, a Get-Metrics command may be used to get the metrics information. The metrics information may include an amount of memory used by the tenant for each cache instance, as shown in column 2 of Table 1 above. The metrics information may also be used to determine the burst memory usage by the tenant at cache cluster level.

At block 730, the memory usage information may be used to determine if it exceeds the memory usage threshold for the tenant. If the memory usage threshold is exceeded, eviction operations may be performed to reduce the memory usage. Eviction may be performed by the metering module 450 described with FIG. 4 using, for example, the command Evict (TenantID, Memory) where “Memory” is a difference between current memory usage and the memory threshold). Eviction may be performed using batch processing.

At block 735, the metering module 450 may use the metrics information to determine the burst memory associated with the tenant. This may be performed by aggregating the metrics information at a cluster level. The metering module 450 may then determine whether the burst memory exceeds the burst memory threshold set for the tenant. If the burst memory threshold is exceeded, cache-write related operations associated with the tenant may be paused. As described with FIG. 6, the metering module 450 may generate and send a pause message to the message bus 508, and an appropriate cache client may use the pause message to pause cache-write related operations. Pausing may include placing the tenant in a pause state. When the tenant is in the pause state, cache-write related operations received from the tenant are dropped and not forwarded to the appropriate cache instance. The pause message may include a pause period.

At block 740, the metering module 450 may generate and send a resume message to the message bus 508. This may be based on the metering module 450 reviewing the list of tenants whose burst memory previously exceeds their burst memory thresholds but are now at or below the burst memory thresholds. Based on receiving the resume message from the message bus 508, the cache client may remove the tenant from the pause state and subsequent cache write operations associated with the tenant may be forwarded to the appropriate cache instance for processing. The flow diagram may stop at block 745. As may be noted from the flow diagram 700, enforcing the memory threshold and the burst memory threshold may be cooperatively performed at the cache instance, by the metering module and by the cache client.

FIG. 8A shows a system diagram 800 illustrating architectural components of an on-demand service environment, in accordance with some embodiments. A client machine located in the cloud 804 (or Internet) may communicate with the on-demand service environment via one or more edge routers 808 and 812. The edge routers may communicate with one or more core switches 820 and 824 via firewall 816. The core switches may communicate with a load balancer 828, which may distribute server load over different pods, such as the pods 840 and 844. The pods 840 and 844, which may each include one or more servers and/or other computing resources, may perform data processing and other operations used to provide on-demand Services. Communication with the pods may be conducted via pod switches 832 and 836. Components of the on-demand service environment may communicate with a database storage system 856 via a database firewall 848 and a database switch 852.

As shown in FIGS. 8A and 8B, accessing an on-demand service environment may involve communications transmitted among a variety of different hardware and/or software components. Further, the on-demand service environment 800 is a simplified representation of an actual on-demand service environment. For example, while only one or two devices of each type are shown in FIGS. 8A and 8B, some embodiments of an on-demand service environment may include anywhere from one to many devices of each type. Also, the on-demand service environment need not include each device shown in FIGS. 8A and 8B, or may include additional devices not shown in FIGS. 8A and 8B.

Moreover, one or more of the devices in the on-demand service environment 800 may be implemented on the same physical device or on different hardware. Some devices may be implemented using hardware or a combination of hardware and software. Thus, terms such as “data processing apparatus,” “machine,” “server” and “device” as used herein are not limited to a single hardware device, but rather include any hardware and software configured to provide the described functionality.

The cloud 804 is intended to refer to a data network or plurality of data networks, often including the Internet. Client machines located in the cloud 804 may communicate with the on-demand service environment to access services provided by the on-demand service environment. For example, client machines may access the on-demand service environment to retrieve, store, edit, and/or process information.

In some embodiments, the edge routers 808 and 812 route packets between the cloud 804 and other components of the on-demand service environment 800. The edge routers 808 and 812 may employ the Border Gateway Protocol (BGP). The BGP is the core routing protocol of the Internet. The edge routers 808 and 812 may maintain a table of IP networks or ‘prefixes’ which designate network reachability among autonomous systems on the Internet.

In one or more embodiments, the firewall 816 may protect the inner components of the on-demand service environment 800 from Internet traffic. The firewall 816 may block, permit, or deny access to the inner components of the on-demand service environment 800 based upon a set of rules and other criteria. The firewall 816 may act as one or more of a packet filter, an application gateway, a stateful filter, a proxy server, or any other type of firewall.

In some embodiments, the core switches 820 and 824 are high-capacity switches that transfer packets within the on-demand service environment 800. The core switches 820 and 824 may be configured as network bridges that quickly route data between different components within the on-demand service environment. In some embodiments, the use of two or more core switches 820 and 824 may provide redundancy and/or reduced latency.

In some embodiments, the pods 840 and 844 may perform the core data processing and service functions provided by the on-demand service environment. Each pod may include various types of hardware and/or software computing resources. An example of the pod architecture is discussed in greater detail with reference to FIG. 8B.

In some embodiments, communication between the pods 840 and 844 may be conducted via the pod switches 832 and 836. The pod switches 832 and 836 may facilitate communication between the pods 840 and 844 and client machines located in the cloud 804, for example via core switches 820 and 824. Also, the pod switches 832 and 836 may facilitate communication between the pods 840 and 844 and the database storage 856.

In some embodiments, the load balancer 828 may distribute workload between the pods 840 and 844. Balancing the on-demand service requests between the pods may assist in improving the use of resources, increasing throughput, reducing response times, and/or reducing overhead. The load balancer 828 may include multilayer switches to analyze and forward traffic.

In some embodiments, access to the database storage 856 may be guarded by a database firewall 848. The database firewall 848 may act as a computer application firewall operating at the database application layer of a protocol stack. The database firewall 848 may protect the database storage 856 from application attacks such as structure query language (SQL) injection, database rootkits, and unauthorized information disclosure.

In some embodiments, the database firewall 848 may include a host using one or more forms of reverse proxy services to proxy traffic before passing it to a gateway router. The database firewall 848 may inspect the contents of database traffic and block certain content or database requests. The database firewall 848 may work on the SQL application level atop the TCP/IP stack, managing applications' connection to the database or SQL management interfaces as well as intercepting and enforcing packets traveling to or from a database network or application interface.

In some embodiments, communication with the database storage system 856 may be conducted via the database switch 852. The multi-tenant database system 856 may include more than one hardware and/or software components for handling database queries. Accordingly, the database switch 852 may direct database queries transmitted by other components of the on-demand service environment (e.g., the pods 840 and 844) to the correct components within the database storage system 856. In some embodiments, the database storage system 856 is an on-demand database system shared by many different organizations. The on-demand database system may employ a multi-tenant approach, a virtualized approach, or any other type of database approach. An on-demand database system is discussed in greater detail with reference to FIGS. 9 and 10.

FIG. 8B shows a system diagram illustrating the architecture of the pod 844, in accordance with one embodiment. The pod 844 may be used to render services to a user of the on-demand service environment 800. In some embodiments, each pod may include a variety of servers and/or other systems. The pod 844 includes one or more content batch servers 864, content search servers 868, query servers 872, file force servers 876, access control system (ACS) servers 880, batch servers 884, and app servers 888. Also, the pod 844 includes database instances 890, quick file systems (QFS) 892, and indexers 894. In one or more embodiments, some or all communication between the servers in the pod 844 may be transmitted via the switch 836.

In some embodiments, the application servers 888 may include a hardware and/or software framework dedicated to the execution of procedures (e.g., programs, routines, scripts) for supporting the construction of applications provided by the on-demand service environment 800 via the pod 844. Some such procedures may include operations for providing the services described herein. The content batch servers 864 may request internal to the pod. These requests may be long-running and/or not tied to a particular customer. For example, the content batch servers 864 may handle requests related to log mining, cleanup work, and maintenance tasks.

The content search servers 868 may provide query and indexer functions. For example, the functions provided by the content search servers 868 may allow users to search through content stored in the on-demand service environment. The Fileforce servers 876 may manage requests information stored in the Fileforce storage 878. The Fileforce storage 878 may store information such as documents, images, and basic large objects (BLOBs). By managing requests for information using the Fileforce servers 876, the image footprint on the database may be reduced.

The query servers 872 may be used to retrieve information from one or more file systems. For example, the query system 872 may receive requests for information from the app servers 888 and then transmit information queries to the NFS 896 located outside the pod. The pod 844 may share a database instance 890 configured as a multi-tenant environment in which different organizations share access to the same database. Additionally, services rendered by the pod 844 may require various hardware and/or software resources. In some embodiments, the ACS servers 880 may control access to data, hardware resources, or software resources.

In some embodiments, the batch servers 884 may process batch jobs, which are used to run tasks at specified times. Thus, the batch servers 884 may transmit instructions to other servers, such as the app servers 888, to trigger the batch jobs. For some embodiments, the QFS 892 may be an open source file system available from Sun Microsystems® of Santa Clara, Calif. The QFS may serve as a rapid-access file system for storing and accessing information available within the pod 844. The QFS 892 may support some volume management capabilities, allowing many disks to be grouped together into a file system. File system metadata can be kept on a separate set of disks, which may be useful for streaming applications where long disk seeks cannot be tolerated. Thus, the QFS system may communicate with one or more content search servers 868 and/or indexers 894 to identify, retrieve, move, and/or update data stored in the network file systems 896 and/or other storage systems.

In some embodiments, one or more query servers 872 may communicate with the NFS 896 to retrieve and/or update information stored outside of the pod 844. The NFS 896 may allow servers located in the pod 844 to access information to access files over a network in a manner similar to how local storage is accessed. In some embodiments, queries from the query servers 822 may be transmitted to the NFS 896 via the load balancer 820, which may distribute resource requests over various resources available in the on-demand service environment. The NFS 896 may also communicate with the QFS 892 to update the information stored on the NFS 896 and/or to provide information to the QFS 892 for use by servers located within the pod 844.

In some embodiments, the pod may include one or more database instances 890. The database instance 890 may transmit information to the QFS 892. When information is transmitted to the QFS, it may be available for use by servers within the pod 844 without requiring an additional database call. In some embodiments, database information may be transmitted to the indexer 894. Indexer 894 may provide an index of information available in the database 890 and/or QFS 892. The index information may be provided to file force servers 876 and/or the QFS 892.

FIG. 9 shows a block diagram of an environment 910 wherein an on-demand database service might be used, in accordance with some embodiments. Environment 910 includes an on-demand database service 916. User system 912 may be any machine or system that is used by a user to access a database user system. For example, any of user systems 912 can be a handheld computing system, a mobile phone, a laptop computer, a work station, and/or a network of computing systems. As illustrated in FIGS. 9 and 10, user systems 912 might interact via a network 914 with the on-demand database service 916.

An on-demand database service, such as system 916, is a database system that is made available to outside users that do not need to necessarily be concerned with building and/or maintaining the database system, but instead may be available for their use when the users need the database system (e.g., on the demand of the users). Some on-demand database services may store information from one or more tenants stored into tables of a common database image to form a multi-tenant database system (MTS). Accordingly, “on-demand database service 916” and “system 916” will be used interchangeably herein. A database image may include one or more database objects. A relational database management system (RDBMS) or the equivalent may execute storage and retrieval of information against the database object(s). Application platform 918 may be a framework that allows the applications of system 916 to run, such as the hardware and/or software, e.g., the operating system. In an implementation, on-demand database service 916 may include an application platform 918 that enables creation, managing and executing one or more applications developed by the provider of the on-demand database service, users accessing the on-demand database service via user systems 912, or third party application developers accessing the on-demand database service via user systems 912.

One arrangement for elements of system 916 is shown in FIG. 9, including a network interface 920, application platform 918, tenant data storage 922 for tenant data 923, system data storage 924 for system data 925 accessible to system 916 and possibly multiple tenants, program code 926 for implementing various functions of system 916, and a process space 928 for executing MTS system processes and tenant-specific processes, such as running applications as part of an application hosting service. Additional processes that may execute on system 916 include database indexing processes.

The users of user systems 912 may differ in their respective capacities, and the capacity of a particular user system 912 might be entirely determined by permissions (permission levels) for the current user. For example, where a call center agent is using a particular user system 912 to interact with system 916, the user system 912 has the capacities allotted to that call center agent. However, while an administrator is using that user system to interact with system 916, that user system has the capacities allotted to that administrator. In systems with a hierarchical role model, users at one permission level may have access to applications, data, and database information accessible by a lower permission level user, but may not have access to certain applications, database information, and data accessible by a user at a higher permission level. Thus, different users may have different capabilities with regard to accessing and modifying application and database information, depending on a user's security or permission level.

Network 914 is any network or combination of networks of devices that communicate with one another. For example, network 914 can be any one or any combination of a LAN (local area network), WAN (wide area network), telephone network, wireless network, point-to-point network, star network, token ring network, hub network, or other appropriate configuration. As the most common type of computer network in current use is a TCP/IP (Transfer Control Protocol and Internet Protocol) network (e.g., the Internet), that network will be used in many of the examples herein. However, it should be understood that the networks used in some embodiments are not so limited, although TCP/IP is a frequently implemented protocol.

User systems 912 might communicate with system 916 using TCP/IP and, at a higher network level, use other common Internet protocols to communicate, such as HTTP, FTP, AFS, WAP, etc. In an example where HTTP is used, user system 912 might include an HTTP client commonly referred to as a “browser” for sending and receiving HTTP messages to and from an HTTP server at system 916. Such an HTTP server might be implemented as the sole network interface between system 916 and network 914, but other techniques might be used as well or instead. In some embodiments, the interface between system 916 and network 914 includes load sharing functionality, such as round-robin HTTP request distributors to balance loads and distribute incoming HTTP requests evenly over a plurality of servers. At least as for the users that are accessing that server, each of the plurality of servers has access to the MTS' data; however, other alternative configurations may be used instead.

In some embodiments, system 916, shown in FIG. 9, implements a web-based customer relationship management (CRM) system. For example, in some embodiments, system 916 includes application servers configured to implement and execute CRM software applications as well as provide related data, code, forms, web pages and other information to and from user systems 912 and to store to, and retrieve from, a database system related data, objects, and Webpage content. With a multi-tenant system, data for multiple tenants may be stored in the same physical database object, however, tenant data typically is arranged so that data of one tenant is kept logically separate from that of other tenants so that one tenant does not have access to another tenant's data, unless such data is expressly shared. In certain embodiments, system 916 implements applications other than, or in addition to, a CRM application. For example, system 916 may provide tenant access to multiple hosted (standard and custom) applications. User (or third party developer) applications, which may or may not include CRM, may be supported by the application platform 918, which manages creation, storage of the applications into one or more database objects and executing of the applications in a virtual machine in the process space of the system 916.

Each user system 912 could include a desktop personal computer, workstation, laptop, PDA, cell phone, or any wireless access protocol (WAP) enabled device or any other computing system capable of interfacing directly or indirectly to the Internet or other network connection. User system 912 typically runs an HTTP client, e.g., a browsing program, such as Microsoft's Internet Explorer® browser, Mozilla's Firefox® browser, Opera's browser, or a WAP-enabled browser in the case of a cell phone, PDA or other wireless device, or the like, allowing a user (e.g., subscriber of the multi-tenant database system) of user system 912 to access, process and view information, pages and applications available to it from system 916 over network 914.

Each user system 912 also typically includes one or more user interface devices, such as a keyboard, a mouse, trackball, touch pad, touch screen, pen or the like, for interacting with a graphical user interface (GUI) provided by the browser on a display (e.g., a monitor screen, LCD display, etc.) in conjunction with pages, forms, applications and other information provided by system 916 or other systems or servers. For example, the user interface device can be used to access data and applications hosted by system 916, and to perform searches on stored data, and otherwise allow a user to interact with various GUI pages that may be presented to a user. As discussed above, embodiments are suitable for use with the Internet, which refers to a specific global internetwork of networks. However, it should be understood that other networks can be used instead of the Internet, such as an intranet, an extranet, a virtual private network (VPN), a non-TCP/IP based network, any LAN or WAN or the like.

According to some embodiments, each user system 912 and all of its components are operator configurable using applications, such as a browser, including computer code run using a central processing unit such as an Intel Pentium® processor or the like. Similarly, system 916 (and additional instances of an MTS, where more than one is present) and all of their components might be operator configurable using application(s) including computer code to run using a central processing unit such as processor system 917, which may include an Intel Pentium® processor or the like, and/or multiple processor units.

A computer program product implementation includes a machine-readable storage medium (media) having instructions stored thereon/in which can be used to program a computer to perform any of the processes of the embodiments described herein. Computer code for operating and configuring system 916 to intercommunicate and to process web pages, applications and other data and media content as described herein are preferably downloaded and stored on a hard disk, but the entire program code, or portions thereof, may also be stored in any other volatile or non-volatile memory medium or device, such as a ROM or RAM, or provided on any media capable of storing program code, such as any type of rotating media including floppy disks, optical discs, digital versatile disk (DVD), compact disk (CD), microdrive, and magneto-optical disks, and magnetic or optical cards, nanosystems (including molecular memory ICs), or any type of media or device suitable for storing instructions and/or data. Additionally, the entire program code, or portions thereof, may be transmitted and downloaded from a software source over a transmission medium, e.g., over the Internet, or from another server, or transmitted over any other conventional network connection (e.g., extranet, VPN, LAN, etc.) using any communication medium and protocols (e.g., TCP/IP, HTTP, HTTPS, Ethernet, etc.). It will also be appreciated that computer code for implementing embodiments can be implemented in any programming language that can be executed on a client system and/or server or server system such as, for example, C, C++, HTML, any other markup language, Java™, JavaScript®, ActiveX®, any other scripting language, such as VBScript, and many other programming languages as are well known may be used. (Java™ is a trademark of Sun Microsystems®, Inc.).

According to some embodiments, each system 916 is configured to provide web pages, forms, applications, data and media content to user (client) systems 912 to support the access by user systems 912 as tenants of system 916. As such, system 916 provides security mechanisms to keep each tenant's data separate unless the data is shared. If more than one MTS is used, they may be located in close proximity to one another (e.g., in a server farm located in a single building or campus), or they may be distributed at locations remote from one another (e.g., one or more servers located in city A and one or more servers located in city B). As used herein, each MTS could include logically and/or physically connected servers distributed locally or across one or more geographic locations. Additionally, the term “server” is meant to include a computing system, including processing hardware and process space(s), and an associated storage system and database application (e.g., OODBMS or RDBMS) as is well known in the art.

It should also be understood that “server system” and “server” are often used interchangeably herein. Similarly, the database object described herein can be implemented as single databases, a distributed database, a collection of distributed databases, a database with redundant online or offline backups or other redundancies, etc., and might include a distributed database or storage network and associated processing intelligence.

FIG. 10 also shows a block diagram of environment 910 further illustrating system 916 and various interconnections, in accordance with some embodiments. FIG. 10 shows that user system 912 may include processor system 912A, memory system 912B, input system 912C, and output system 912D. FIG. 10 shows network 914 and system 916. FIG. 10 also shows that system 916 may include tenant data storage 922, tenant data 923, system data storage 924, system data 925, User Interface (UI) 1030, Application Program Interface (API) 1032, PL/SOQL 1034, save routines 1036, application setup mechanism 1038, applications servers 10001-1000N, system process space 1002, tenant process spaces 1004, tenant management process space 1010, tenant storage area 1012, user storage 1014, and application metadata 1016. In other embodiments, environment 910 may not have the same elements as those listed above and/or may have other elements instead of, or in addition to, those listed above.

User system 912, network 914, system 916, tenant data storage 922, and system data storage 924 were discussed above in FIG. 9. Regarding user system 912, processor system 912A may be any combination of processors. Memory system 912B may be any combination of one or more memory devices, short term, and/or long term memory. Input system 912C may be any combination of input devices, such as keyboards, mice, trackballs, scanners, cameras, and/or interfaces to networks. Output system 912D may be any combination of output devices, such as monitors, printers, and/or interfaces to networks. As shown by FIG. 10, system 916 may include a network interface 920 (of FIG. 9) implemented as a set of HTTP application servers 1000, an application platform 918, tenant data storage 922, and system data storage 924. Also shown is system process space 1002, including individual tenant process spaces 1004 and a tenant management process space 1010. Each application server 1000 may be configured to tenant data storage 922 and the tenant data 923 therein, and system data storage 924 and the system data 925 therein to serve requests of user systems 912. The tenant data 923 might be divided into individual tenant storage areas 1012, which can be either a physical arrangement and/or a logical arrangement of data. Within each tenant storage area 1012, user storage 1014 and application metadata 1016 might be similarly allocated for each user. For example, a copy of a user's most recently used (MRU) items might be stored to user storage 1014. Similarly, a copy of MRU items for an entire organization that is a tenant might be stored to tenant storage area 1012. A UI 1030 provides a user interface and an API 1032 provides an application programmer interface to system 916 resident processes to users and/or developers at user systems 912. The tenant data and the system data may be stored in various databases, such as Oracle™ databases.

Application platform 918 includes an application setup mechanism 1038 that supports application developers' creation and management of applications, which may be saved as metadata into tenant data storage 922 by save routines 1036 for execution by subscribers as tenant process spaces 1004 managed by tenant management process 1010 for example. Invocations to such applications may be coded using PL/SOQL 34 that provides a programming language style interface extension to API 1032. A detailed description of some PL/SOQL language embodiments is discussed in commonly assigned U.S. Pat. No. 7,730,478, titled METHOD AND SYSTEM FOR ALLOWING ACCESS TO DEVELOPED APPLICATIONS VIA A MULTI-TENANT ON-DEMAND DATABASE SERVICE, by Craig Weissman, filed Sep. 21, 2007, which is hereby incorporated by reference in its entirety and for all purposes. Invocations to applications may be detected by system processes, which manage retrieving application metadata 1016 for the subscriber making the invocation and executing the metadata as an application in a virtual machine.

Each application server 1000 may be communicably coupled to database systems, e.g., having access to system data 925 and tenant data 923, via a different network connection. For example, one application server 10001 might be coupled via the network 914 (e.g., the Internet), another application server 1000N-1 might be coupled via a direct network link, and another application server 1000N might be coupled by yet a different network connection. Transfer Control Protocol and Internet Protocol (TCP/IP) are typical protocols for communicating between application servers 1000 and the database system. However, other transport protocols may be used to optimize the system depending on the network interconnect used.

In certain embodiments, each application server 1000 is configured to handle requests for any user associated with any organization that is a tenant. Because it is desirable to be able to add and remove application servers from the server pool at any time for any reason, there is preferably no server affinity for a user and/or organization to a specific application server 1000. In some embodiments, therefore, an interface system implementing a load balancing function (e.g., an F5 Big-IP load balancer) is communicably coupled between the application servers 1000 and the user systems 912 to distribute requests to the application servers 1000. In some embodiments, the load balancer uses a least connections algorithm to route user requests to the application servers 1000. Other examples of load balancing algorithms, such as round robin and observed response time, also can be used. For example, in certain embodiments, three consecutive requests from the same user could hit three different application servers 1000, and three requests from different users could hit the same application server 1000. In this manner, system 916 is multi-tenant, wherein system 916 handles storage of, and access to, different objects, data and applications across disparate users and organizations.

As an example of storage, one tenant might be a company that employs a sales force where each call center agent uses system 916 to manage their sales process. Thus, a user might maintain contact data, leads data, customer follow-up data, performance data, goals and progress data, etc., all applicable to that user's personal sales process (e.g., in tenant data storage 922). In an example of a MTS arrangement, since all of the data and the applications to access, view, modify, report, transmit, calculate, etc., can be maintained and accessed by a user system having nothing more than network access, the user can manage his or her sales efforts and cycles from any of many different user systems. For example, if a call center agent is visiting a customer and the customer has Internet access in their lobby, the call center agent can obtain critical updates as to that customer while waiting for the customer to arrive in the lobby.

While each user's data might be separate from other users' data regardless of the employers of each user, some data might be organization-wide data shared or accessible by a plurality of users or all of the users for a given organization that is a tenant. Thus, there might be some data structures managed by system 916 that are allocated at the tenant level while other data structures might be managed at the user level. Because an MTS might support multiple tenants including possible competitors, the MTS should have security protocols that keep data, applications, and application use separate. Also, because many tenants may opt for access to an MTS rather than maintain their own system, redundancy, up-time, and backup are additional functions that may be implemented in the MTS. In addition to user-specific data and tenant specific data, system 916 might also maintain system level data usable by multiple tenants or other data. Such system level data might include industry reports, news, postings, and the like that are sharable among tenants.

In certain embodiments, user systems 912 (which may be client machines/systems) communicate with application servers 1000 to request and update system-level and tenant-level data from system 916 that may require sending one or more queries to tenant data storage 922 and/or system data storage 924. System 916 (e.g., an application server 1000 in system 916) automatically generates one or more SQL statements (e.g., SQL queries) that are designed to access the desired information. System data storage 924 may generate query plans to access the requested data from the database.

Each database can generally be viewed as a collection of objects, such as a set of logical tables, containing data fitted into predefined categories. A “table” is one representation of a data object, and may be used herein to simplify the conceptual description of objects and custom objects according to some embodiments. It should be understood that “table” and “object” may be used interchangeably herein. Each table generally contains one or more data categories logically arranged as columns or fields in a viewable schema. Each row or record of a table contains an instance of data for each category defined by the fields. For example, a CRM database may include a table that describes a customer with fields for basic contact information such as name, address, phone number, fax number, etc. Another table might describe a purchase order, including fields for information such as customer, product, sale price, date, etc. In some multi-tenant database systems, standard entity tables might be provided for use by all tenants. For CRM database applications, such standard entities might include tables for account, contact, lead, and opportunity data, each containing pre-defined fields. It should be understood that the word “entity” may also be used interchangeably herein with “object” and “table”.

In some multi-tenant database systems, tenants may be allowed to create and store custom objects, or they may be allowed to customize standard entities or objects, for example by creating custom fields for standard objects, including custom index fields. U.S. Pat. No. 7,779,039, titled CUSTOM ENTITIES AND FIELDS IN A MULTI-TENANT DATABASE SYSTEM, by Weissman, et al., and which is hereby incorporated by reference in its entirety and for all purposes, teaches systems and methods for creating custom objects as well as customizing standard objects in a multi-tenant database system. In some embodiments, for example, all custom entity data rows are stored in a single multi-tenant physical table, which may contain multiple logical tables per organization. In some embodiments, multiple “tables” for a single customer may actually be stored in one large table and/or in the same table as the data of other customers.

These and other aspects of the disclosure may be implemented by various types of hardware, software, firmware, etc. For example, some features of the disclosure may be implemented, at least in part, by machine-program product that include program instructions, state information, etc., for performing various operations described herein. Examples of program instructions include both machine code, such as produced by a compiler, and files containing higher-level code that may be executed by the computer using an interpreter. Examples of machine-program product include, but are not limited to, magnetic media such as hard disks, floppy disks, and magnetic tape; optical media such as CD-ROM disks; magneto-optical media; and hardware devices that are specially configured to store and perform program instructions, such as read-only memory devices (“ROM”) and random access memory (“RAM”).

While one or more embodiments and techniques are described with reference to an implementation in which a service cloud console is implemented in a system having an application server providing a front end for an on-demand database service capable of supporting multiple tenants, the one or more embodiments and techniques are not limited to multi-tenant databases nor deployment on application servers. Embodiments may be practiced using other database architectures, i.e., ORACLE®, DB2® by IBM and the like without departing from the scope of the embodiments claimed.

Any of the above embodiments may be used alone or together with one another in any combination. Although various embodiments may have been motivated by various deficiencies with the prior art, which may be discussed or alluded to in one or more places in the specification, the embodiments do not necessarily address any of these deficiencies. In other words, different embodiments may address different deficiencies that may be discussed in the specification. Some embodiments may only partially address some deficiencies or just one deficiency that may be discussed in the specification, and some embodiments may not address any of these deficiencies.

While various embodiments have been described herein, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of the present application should not be limited by any of the embodiments described herein, but should be defined only in accordance with the following and later-submitted claims and their equivalents. 

What is claimed is:
 1. A method comprising: associating, by a database system, a tenant of a plurality of tenants in a multi-tenant environment with a cache cluster formed by a group of cache instances; associating, by the database system, a memory threshold and a burst memory threshold with the tenant, the memory threshold being an amount of usable memory set for the associated tenant and the burst memory threshold being an amount of usable burst memory set for the associated tenant, the memory threshold and the burst memory threshold being specific to the associated tenant; enabling, by the database system, each of the cache instances in the cache cluster associated with the tenant to collect metrics information based on the tenant accessing the cache cluster by performing cache-write related operations to one or more of the cache instances in the cache cluster, the memory usage information and burst memory usage information of the cache cluster by the tenant being determined by aggregating the metrics information collected by the group of cache instances in the cache cluster; and controlling, by the database system, usage of the cache cluster by the tenant based on comparing the memory usage information with the memory threshold, comparing the burst memory usage information with the burst memory threshold and performing eviction operations when the memory usage information violates the memory threshold.
 2. The method of claim 1, wherein the eviction operations are performed until the memory usage information stops violating the memory threshold.
 3. The method of claim 2, wherein controlling the usage of the cache cluster by the tenant based on comparing the burst memory usage information with the burst memory threshold comprises pausing the cache-write related operations associated with the tenant.
 4. The method of claim 3, wherein the cache-write related operations are paused for a pause period.
 5. The method of claim 4, wherein controlling the usage of the cache cluster by the tenant based on comparing the burst memory usage information with the burst memory threshold comprises resuming the cache-write related operations associated with the tenant based on expiration of the pause period or based on determining that the burst memory usage information stops violating the burst memory threshold.
 6. The method of claim 5, further comprising: performing, by the database system, the eviction operations on the cache cluster based on an eviction policy.
 7. A computer program product comprising computer-readable program code to be executed by one or more processors when retrieved from a non-transitory computer-readable medium, the program code including instructions to: associate a tenant in a multi-tenant environment with a cache cluster formed by a group of cache instances; associate a memory threshold and a burst memory threshold with the tenant, the memory threshold being an amount of usable memory set for the associated tenant and the burst memory threshold being an amount of usable burst memory set for the associated tenant, the memory threshold and the burst memory threshold being specific to the associated tenant; enable each of the cache instances in the cache cluster associated with the tenant to collect metrics information based on the tenant accessing the cache cluster by performing cache-write related operations to one or more of the cache instances in the cache cluster, the memory usage information and burst memory usage information of the cache cluster by the tenant being determined by aggregating the metrics information collected by the group of cache instances in the cache cluster; and control usage of the cache cluster by the tenant based on comparing the memory usage information with the memory threshold, comparing the burst memory usage information with the burst memory threshold and performing eviction operations when the memory usage information violates the memory threshold.
 8. The computer program product of claim 7, wherein the eviction operations are performed until the memory usage information stops violating the memory threshold.
 9. The computer program product of claim 8, wherein controlling the usage of the cache cluster by the tenant based on comparing the burst memory usage information with the burst memory threshold comprises pausing the cache-write related operations associated with the tenant.
 10. The computer program product of claim 9, wherein the cache-write related operations are paused for a pause period.
 11. The computer program product of claim 10, wherein controlling the usage of the cache cluster by the tenant based on comparing the burst memory usage information with the burst memory threshold comprises resuming cache-write related operations associated with the tenant based on expiration of the pause period or based on determining that the burst memory usage information stops violating the burst memory threshold.
 12. The computer program product of claim 11, further comprising instructions to perform the eviction operations on the cache cluster based on an eviction policy.
 13. A system comprising: one or more processors; and a non-transitory computer readable medium storing a plurality of instructions, which when executed, cause the one or more processors of a first server computing system to: associate a tenant in a multi-tenant environment with a cache cluster formed by a group of cache instances; associate a memory threshold and a burst memory threshold with the tenant, the memory threshold being an amount of usable memory set for the associated tenant and the burst memory threshold being an amount of usable burst memory set for the associated tenant; enable each of the cache instances in the cache cluster associated with the tenant to collect metrics information based on the tenant accessing the cache cluster by performing cache-write related operations to one or more of the cache instances in the cache cluster, the memory usage information and burst memory usage information of the cache cluster by the tenant being determined by aggregating the metrics information collected by the group of cache instances in the cache cluster; and control usage of the cache cluster by the tenant based on comparing the memory usage information with the memory threshold, comparing the burst memory usage information with the burst memory threshold and performing eviction operations when the memory usage information violates the memory threshold.
 14. The system of claim 13, wherein the eviction operations are performed until the memory usage information stops violating the memory threshold.
 15. The system of claim 14, wherein controlling the usage of the cache cluster by the tenant based on comparing the burst memory usage information with the burst memory threshold comprises pausing the cache-write related operations associated with the tenant.
 16. The system of claim 15, wherein the cache-write related operations are paused for a pause period.
 17. The system of claim 16, wherein controlling the usage of the cache cluster by the tenant based on comparing the burst memory usage information with the burst memory threshold comprises resuming cache-write related operations associated with the tenant based on expiration of the pause period or based on determining that the burst memory usage information stops violating the burst memory threshold.
 18. The system of claim 17, further comprising instructions to perform the eviction operations on the cache cluster based on an eviction policy. 